Devices of this type are well known in the art, including a device as disclosed in U.S. Design Patent Des. 205,327, issued July 19, 1986 to Lukas, which is in the form of dual inflatable annular air chambers adapted to be positioned over and encircle a user's upper arm, the air chambers being connected to each other in parallel relation and each having an inflation nipple. The advantage of such a construction is that reduced but still adequate buoyancy is provided to the user in the event of puncturing of one of the air chambers, or, the accidental dislodgement of the closure plug of the inflation nipple associated with that chamber.
Such devices closely embrace the user's upper arm with a frictional grip to minimize the tendency of the device to slip longitudinally off the user's arm when in a straightened position. However, if the user's arm is wet, the film of water on the user's arm provides an efficient lubricant for the material from which the device has been formed, typically polyvinylchloride sheeting. This allows for the slippage of the device longitudinally of the user's arm.
Also, such a device is somewhat difficult to grip in the event that a supervisor is required to give quick assistance to the user, who possibly is an inexperienced swimmer such as a learning child.